The paper presents the development of a numerical algorithm capable of simulating the main ash formation mechanisms during the combustion of a coal particle, i.e coalescence of included minerals in the coal particle and fragmentation of the excluded ones. This numerical model can be implemented in any CFD code following an Eulerian approach for the prediction of the main characteristics of the induced multiphase flow withinany furnace. This work succeeds in developing and implementing innovative kernels describing the aforementioned mechanisms, considering the p.s.d of each mineral in the coal particle, with an output the corresponding p.s.d of the ash particles not only at the exit of the furnace, but also at any region, which is crucial for the ash depositions mechanisms. The methodology applied can be integrated into ash formation models, coupling the governing mechanisms with hydrodynamics and combustion. Furthermore, it provides information about the effect of coalescence andbreakage phenomena on the time evolution of the ash formation mechanism. In this way, a more comprehensive description of the ash formation mechanisms is achieved, which can be coupled with respective ash deposition models. Finally, the new model describing the main ash formation mechanisms, i.e. coalescence of included minerals and fragmentation of excluded ones interacting with theinduced velocity and temperature field was first formulated and implemented in a commercial code, namely FluentTM using as an input CCSEM analysis of a given fuels and comparison of the different ash particles size ranges formed from a drop tube furnace where ash was collected by a cascading impactor.